Fig. 1

Oligodendrocytes are closely and predominantly associated with capillaries in the neocortical gray matter

(A) Representative images of vOLs and the major vascular components: endothelial cells (CD31), pericytes (CD13) and basement membrane (collagen-IV), and corresponding 3D reconstructions. Oligodendrocyte cell bodies (cyan) appear directly associated with the vasculature (red). (B) Normalized pixel intensity plots used for quantifying the distance between vasculature and oligodendrocytes. Labeling of either CD31, CD13 or collagen-IV shows sub-micrometer distances between blood vessel components and oligodendrocyte cell body. Maximum peaks of the immunosignal (red and black arrowheads) were used to quantify spacing between immunosignals. (C) Quantification based on (B) reveals the shortest distance for collagen-IV compared to CD31 and CD13, consistent with blood vessel anatomy (Kruskal-Wallis test, p = 0.0001, n = 12 cells for CD31, n = 17 cells for collagen-IV, n = 29 cells for CD13, each from n = 4 mice). (D) Quantification of oligodendrocytes on vascular bifurcations from the total population of vOLs (Unpaired t-test, p = 0.72, n = 6 mice/area). (E) High magnification image of a myelin sheath connected to a vOL. Arrowheads indicate the cell process linking the myelin sheath to the cell body, arrows mark the extension of the internode. The majority of the blood vessel was cut for display. (F) Distribution of vOLs on different sized blood vessels shows that the majority is associated with vessels < 8 μm, presumably capillaries (n = 6 mice). (G) Representative images of oligodendrocytes on transferrin receptor negative (arterioles) and positive (capillaries and venules) blood vessels. Arrows point to oligodendrocyte cell bodies. A: arteriole, Cap: capillary. (H) Quantification of blood vessel types reveals that the majority of vOLs are located on transferrin-positive capillaries (n = 4 mice).